Optoelectronic sensor and method for detecting objects

Abstract

An optoelectronic sensor ( 10 ), in particular a laser scanner, is provided which comprises a light transmitter ( 12 ) for transmitting a light beam ( 16 ) having a beam profile ( 28 ) elongated in a line direction into a monitored plane ( 26 ), a light receiver ( 34 ) for generating a received signal from the light bream ( 30 ) remitted by objects in the monitored plane ( 26 ), a movable deflection unit ( 24 ) for the periodic deflection of the light beam ( 16, 30 ) to scan the monitored plane ( 26 ) in the course of the movement and an evaluation unit ( 42 ) for detecting the objects with reference to the received signal. The laser scanner has an optical beam rotation element ( 20 ) which is disposed after the light transmitter ( 12 ) and which can tilt the line direction of a light beam ( 16 ) passing through.

The invention claimed is: 
     
       1. An optoelectronic sensor ( 10 ) which comprises a light transmitter ( 12 ) for transmitting a light beam ( 16 ) having a beam profile ( 28 ) elongated in a line direction into a monitored zone ( 26 ), a light receiver ( 34 ) for generating a received signal from the light beam ( 30 ) remitted by objects in the monitored plane ( 26 ), a movable deflection unit ( 24 ) for the periodic deflection of the light beam ( 16 ,  30 ) to scan the monitored plane ( 26 ) in the course of the movement and an evaluation unit ( 42 ) for detecting the objects with reference to the received signal, wherein the sensor further comprises an optical beam rotation element ( 20 ) which is arranged after the light transmitter ( 12 ) and is configured to rotate an incident light beam ( 16 ) with arbitrary orientation of the line direction such that the transmitted light beam ( 16 ) always exits with one and the same uniform orientation of the line direction in order to compensate the change in orientation of the light spot in the monitoring zone ( 26 ) induced by the movable deflection unit ( 24 ). 
     
     
       2. A sensor  10  in accordance with  claim 1 , wherein the sensor is a laser scanner. 
     
     
       3. A sensor ( 10 ) in accordance with  claim 1 , wherein the beam rotation element ( 20 ) is designed such that the transmitted light beam ( 16 ) is orientated with its line direction in the monitored plane ( 26 ) independently of the position of the movable deflection unit ( 24 ) perpendicular to the monitored plane ( 26 ). 
     
     
       4. A sensor ( 10 ) in accordance with  claim 1 ,
 wherein the movable deflection unit ( 24 ) is a rotating mirror which rotates. 
 
     
     
       5. A sensor ( 10 ) in accordance with  claim 1 ,
 wherein the beam rotation element ( 20 ) is installed to move along with the deflection unit ( 24 ), and/or wherein the beam rotation element is connected rigidly or via a transmission element to the deflection unit ( 24 ). 
 
     
     
       6. A sensor ( 10 ) in accordance with  claim 1 ,
 wherein the beam rotation element ( 20 ) is arranged in the beam path of the transmitted light beam ( 16 ) between the light transmitter ( 12 ) and the deflection unit ( 24 ). 
 
     
     
       7. A sensor ( 10 ) in accordance with  claim 1 ,
 wherein the light transmitter ( 12 ) has a laser light source and a collimator lens ( 14 ). 
 
     
     
       8. A sensor ( 10 ) in accordance with  claim 1 ,
 wherein the beam rotation element ( 20 ) has a tandem cylindrical lens arrangement ( 202 ,  204 ,  206 ) which includes a substrate ( 202 ) having at least one respective cylindrical lens ( 202 ) on the front side and at least one cylindrical lens ( 204 ) on the rear side of the substrate ( 202 ). 
 
     
     
       9. A sensor ( 10 ) in accordance with  claim 8 ,
 wherein the cylindrical lenses ( 204 ) have a focal length at the front side at which the focus lies in the plane of the cylindrical lenses ( 206 ) on the rear side; and/or wherein the cylindrical lenses ( 204 ,  206 ) are aligned parallel to one another. 
 
     
     
       10. A sensor ( 10 ) in accordance with  claim 8 ,
 wherein the tandem cylindrical lens arrangement ( 202 ,  204 ,  206 ) is orientated so that the exiting light beam ( 16 ) is perpendicular to the monitored plane ( 26 ) with its line direction in the monitored plane ( 26 ). 
 
     
     
       11. A sensor ( 10 ) in accordance with  claim 1 ,
 wherein the beam rotation element ( 20 ) has a prism, and/or wherein the rotation element ( 20 ) is a Dove prism. 
 
     
     
       12. A sensor ( 10 ) in accordance with  claim 1 ,
 wherein the beam rotation element ( 20 ) has a diffractive optical element or a Fresnel lens. 
 
     
     
       13. A sensor ( 10 ) in accordance with  claim 1 ,
 wherein at least one lens ( 22 ) is disposed after the beam rotation element ( 20 ). 
 
     
     
       14. A sensor ( 10 ) in accordance with  claim 1 ,
 which is designed as a distance measuring device, wherein the light transit time between the transmission and reception of the light beam ( 16 ,  30 ) can be determined in the evaluation unit ( 42 ) and the distance of an object can be determined from this; and/or 
 wherein an angle measuring unit ( 38 ,  40 ) is provided by means of which the angular position of the deflection unit ( 24 ) can be detected so that two-dimensional position coordinates are available for detected objects in the monitored plane ( 26 ). 
 
     
     
       15. A sensor ( 10 ) in accordance with  claim 1 ,
 which is designed as a safety scanner having a safety output ( 44 ) in that it can be determined in the evaluation unit ( 42 ) whether an object is located in a protected field within the monitored plane ( 26 ) and a safety-directed switch-off signal can thereupon be output via the safety output ( 44 ). 
 
     
     
       16. A method of detecting objects in a monitored plane ( 26 ), wherein a light beam ( 16 ) with a beam profile ( 28 ) elongated in a line direction is transmitted by a light transmitter ( 12 ) into the monitored plane ( 26 ) and a received signal is formed in a light receiver ( 34 ) from the light beam ( 30 ) remitted by objects in the monitored plane ( 26 ), wherein the monitored plane ( 26 ) is scanned by periodical deflection of the light beam ( 16 ,  30 ) at a movable deflection unit ( 24 ) and the objects are detected with reference to the received signal,
 wherein an incident light beam ( 16 ) is rotated with arbitrary orientation of the line direction such that the transmitted light beam ( 16 ) always exits with one and the same uniform orientation of the line direction in order to compensate the change in orientation of the light spot in the monitoring zone ( 26 ) induced by the movable deflection unit ( 24 ).